However, the revelations on Wednesday that he might give the information to doping authorities could have a huge impact on the footballing landscape if major players, teams or organisations are involved.

Fuentes told reporters attending the trial: "If they [anti-doping authorities] believe that I am useful and they ask me [to co-operate] I would consider it and I would be ready.

"What I don't know is if what I could contribute would be worth anything to them or not.

"This would be in exchange for mutual collaboration. If the list was necessary within this collaboration, they would get it."

The doctor denied he was trying to hint at a plea bargain in a trial which has been under way since January, when quotes first emerged from Fuentes confirming he had footballing clients.

Doping issues have been known in cycling for decades though the sport now considers itself to be clean, but drug bans in football are uncommon.